The present invention relates to a panel for a cathode ray tube (CRT), and more particularly, to a CRT panel and a method for manufacturing the same in which the entire area of a viewing screen is uniformly illuminated.
CRTs generally comprise a panel defining a front exterior of the CRT, and a funnel joined to the panel to define a rear exterior of the CRT. The funnel includes a neck which is formed on an end of the funnel opposite to the end joined to the panel, and an electron gun is provided in the neck of the funnel. The panel includes a display portion defining a distal end of the panel, a lateral wall curved and extending toward the funnel to be joined to the same, a phosphor screen provided adjacent to the display portion within the CRT, a mask frame connected to the lateral wall of the panel, and a shadow mask joined to the mask frame at a predetermined distance from the phosphor screen.
The electron gun radiates red (R), green (G) and blue (B) electron beams in a direction toward the panel. The RGB electron beams are controlled by image signals such that the beams are deflected to specific pixels by an electrical field generated by a deflection yoke, the deflection yoke being disposed on an outer circumference of the funnel. The deflected electron beams pass through apertures of the shadow mask to land on specific RGB phosphor pixels of the phosphor screen such that color selection of the electron beams by the shadow mask is realized. Accordingly, the RGB phosphors of the phosphor screen are illuminated for the display of color images.
As shown in FIG. 4, illustrating the conventional shadow mask 1 having apertures 3 formed therein, spaces between the apertures 3 become increasingly larger toward a periphery of the shadow mask 1. That is, positions of the apertures 3 on the shadow mask 1 where the electron beams land become spaced farther apart toward outer edges of the same. Such a configuration corresponds to incremental increases in the degree of deflection of the electron beams by the deflection yoke toward the periphery of the shadow mask 1. Without this structure, the electron beams would pass through their designated apertures 3 at the center of the shadow mask 1, but not at the peripheries of the same.
However, with the formation of the shadow mask as in the above, the RGB phosphor pixels on the phosphor screen must also be formed in their dot or stripe matrices with spaces corresponding to the spaces formed between the apertures of the shadow mask. Accordingly, the area of a light-absorbing black matrix layer formed between the dot- or stripe-type phosphor pixels enlarges such that brightness is increasingly reduced toward the peripheries of the display portion.
Therefore, the illumination over the surface of the viewing screen becomes uneven with the center of the viewing screen being brighter than the outer peripheral portions of the same. Assuming that the degree of darkness at the center of the phosphor screen is indexed at 100, the degree of darkness at the periphery of the phosphor screen is 120. In the stripe-type CRT, this translates into a 50% reduction in brightness at the peripheries of the display, whereas a 30% decrease in peripheral brightness results in the dot-type CRT.
Further, as CRTs become increasingly flatter, following advances made in CRT technology, the above problem worsens. That is, differences in the spaces between the apertures of the shadow mask from the center to the peripheries of the same, and therefore the spaces between the phosphor pixels of the phosphor layer, increase as the CRT becomes flatter.
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a CRT panel and a method for manufacturing the same in which the entire area of a viewing screen is uniformly illuminated.
To achieve the above object, the present invention provides a CRT panel and a method for manufacturing the same. The CRT panel is made of clear glass and includes a display portion defining a distal end of the panel; a curved lateral wall extending from the display portion toward a funnel of the CRT, ends of the lateral wall being joined to the funnel; a phosphor screen formed on an inside surface of the display portion, the phosphor screen including RGB phosphor pixels and a black matrix layer between the RGB phosphor pixels; and light transmittance compensating means for compensating for differences in brightness of the phosphor screen, the light transmittance compensating means being provided on an outside surface of the display portion and having varying levels of light transmittivity over its surface.
According to a feature of the present invention, the light transmittance compensating means comprises a tinted coating layer colored such that it is dark at a center and gradually becomes increasingly lighter toward a periphery thereof.
According to another feature of the present invention, the main element of the tinted coating layer is a resin-based polymer compound, and pigmentation is added to the resin-based polymer compound. It is preferable that the resin-based polymer compound is tetraethyl o-silicate.
According to yet another feature of the present invention, the coloring for the tinted coating layer is made of one or more materials selected from the group consisting of cobalt oxide, nickel oxide, carbon black and graphite. The tinted coating layer gradually becomes increasingly lighter toward the periphery in direct proportion to an increase of the black matrix area of the phosphor screen toward a periphery of the same.
The method of manufacturing the CRT panel comprises the steps of (a) forming a phosphor screen on an inner surface of the panel by sequentially depositing a black matrix material and RGB phosphor material; and (b) forming light transmittance compensating means on an outer surface of the panel, the light transmittance compensating means having a gradating level of light transmittivity over its surface.
According to a feature of the present invention, in step (a), a tinted coating layer is formed on the outer surface of the panel, the tinted coating layer being increasingly lighter in color toward the outer periphery of a display portion of the panel. One side of the tinted coating layer is coated with an adhesive, which is then applied to the outer surface of the display portion of the panel.
In another aspect, the tinted coating layer is formed on the outer surface of the panel using a printing process.